This invention relates generally to display panels and more particularly to a unique light pipe of the type used in backlighting for the distribution of light in light emitting display panels.
Still more particularly, the invention relates to a light pipe having quadraspherical depressions which are varied in size and proximity to one another across the light pipe surface.
Panel assemblies are commonly used in visual displays in a variety of applications to provide distribution of light in a pattern that is favorable for viewing of the display. It is common. practice for light emitting panel assemblies of this type to include a clear plastic panel known as a light pipe. The light pipe is typically an acrylic or polycarbonate panel into which light is directed through the panel edge. The light that is introduced into the light pipe reflects from a reflective surface such as a light colored surface or a molded in detail. The reflected light escapes from the light pipe and is used for illumination in the display assembly.
Various techniques have been used to enhance the efficiency of the light pipe so that as much light as possible is directed toward the viewer. Equally important is even distribution of the light to assure uniformity in the intensity of the light across the light pipe surface. Among the techniques that have been used to enhance the efficiency and uniformity of the light is the practice of providing small slots in the back surface of the light pipe to serve as reflectors. As disclosed in U.S. Pat. No. 5,005,108 to Pristash et al. and U.S. Pat. Nos. 5,613,751 and 5,618,096 to Parker et al., disruptions or deformities in the panel have also been proposed. While all of these techniques provide results that are satisfactory in many respects, there is considerable room for improvement in the areas of efficiency and uniformity.
The present invention is directed to a light pipe having a plurality of quadraspherical depressions which provide increased efficiency in the use of light and which effect distribution of the light in a uniform manner across the light pipe surface.
In accordance with the invention, a light pipe for use in a display panel backlight takes the form of a clear plastic panel. Quadraspherical depressions are provided in at least one face of the panel to enhance the efficiency and the uniformity of the light distribution. When incorporated in a backlight panel assembly, the light pipe panel is sandwiched between a base panel and a display cover panel. Light emitting diodes or another light source applies light into the edge of the light pipe panel.
Preferably, the depressions are arranged in rows. Along each row, the depressions vary in size and may become progressively larger from one end of each row to the other end. Also, the depressions may vary in their proximity to the adjacent depressions in each row. In particular, the depressions in each row may be progressively closer together from one end of the row to the opposite end. This pattern has been found to be efficient in distributing the light, and the unique quadraspherical shape of each of the depressions enhances the overall efficiency and uniformity of light distribution.